1. Field of the Invention
This invention relates to a noise protection sheet which is stuck on an electronic component mounted on a circuit board and serves to suppress the noise generated from the electronic component, its mounting apparatus and its mounting method.
2. Description of the Related Art
Traditionally, an electronic appliance such a personal computer, a portable telephone, etc. includes a circuit board on which electronic components such an IC chip C, a resistor, etc. are mounted. On the surface of the circuit board 31, a wiring pattern (not shown) and a land serving as a grounding terminal are formed. The IC chip generates noise from itself to have an adverse effect of causing a surrounding electronic component to malfunction, etc.
One example of countermeasure for such a noise problem is to stick a metallic sheet of e.g. copper on an upper surface of the IC chip and connect the metallic sheet to the land 32 serving as a grounding terminal for the circuit board 31 by e.g. soldering. Otherwise, a conductive wire connected to the metallic sheet is secured to a terminal for attachment by screws. In this way, the IC chip C is shielded electromagnetically by the metallic sheet so that the noise generated from the IC is suppressed.
However, the operation of sticking the metallic sheet on the IC chip and soldering it is generally carried out manually. This takes a long time for this operation and is problematic in the working efficiency. Further, the manual operation gives rise to a fear of causing e.g. peeling off of a sheet. Accordingly, the conventional noise sheet is not excellent in quality.
This invention has been accomplished under the above circumstance.
An object of this invention is to provide a noise protection sheet which can effectively solve a noise problem in an electronic component.
Another object of this invention is to provide an apparatus for mounting such a noise protection sheet.
Still another object of this invention is to provide a method of mounting such a noise protection sheet.
In order to attain the above object, the following techniques are proposed.
In accordance with the first aspect of this invention, there is provided a noise protection sheet stuck on electronic components loaded on a circuit board to control the noise generated from the electronic components, comprising:a metallic sheet, and insulating films which sandwiches the metallic sheet from both front and rear surfaces thereof, wherein the metallic sheet has, at its one end, an extending portion to be connected to a grounding terminal for the circuit board.
Concretely, the other area of the metallic sheet than the extending portion is covered with the insulating films and the extending portion thereof is externally exposed.
In accordance with the noise protection sheet according to this invention, the metallic sheet is sandwiched between the insulating films. The noise protection sheet is stuck onto the upper surface of e.g. an electronic component. The extending portion formed at the one end of the metallic sheet is connected to the grounding terminal for the circuit board. For this reason, while the insulating films keep insulation from the electronic component, the entire metallic sheet can be surely communicated with the grounding terminal through the extending portion so that an excellent shielding effect can be shown. This suppresses the adverse effect of the electronic component to the environment. Further, the sheet, which is metallic, has certain rigidity so that it can be easily handled by a working machine. For this reason, the mounting operation of the noise protection sheet on the electronic component can be automated. This improves the efficiency of the mounting operation.
In another preferred embodiment, the extending portion has a through-hole from which a solder fillet formed on the land elutes when the extending potion is soldered on the land. Therefore, if the extending portion is pressed from above by a head of e.g. a pulse heater, the solder fillet melts and elutes through the through-hole. As a result, the extending portion can be soldered to the grounding terminal. In this way, the soldering operation using the pulse heater can be automated, and assured, thereby improving the quality of the noise protection sheet.
In still another preferred embodiment, the extending portion is bent so as to fit the shape of the electronic component when it is stuck on the electronic component. Therefore, the tip of the extending portion is kept substantially in parallel to the surface of the circuit board so that the soldering operation can be more easily carried out than the case where the soldering operation is carried out with the extending portion being pressed down from above.
In accordance with the second aspect of this invention, there is provided an apparatus for mounting an noise protection sheet on an electronic component loaded on a circuit board, the noise protection sheet with a metallic sheet sandwiched by insulating films from its both front and rear surfaces, comprising:
carrying means for carrying the noise protection sheet held on a carrier tape;
moving means for chucking the noise protection sheet and moving it from the carrier tape onto the electronic component on the circuit board; and
soldering means for soldering an extending portion formed at the one end of the metallic sheet to a grounding terminal for the circuit board.
In accordance with the mounting apparatus having the above configuration, where the noise protection sheet is mounted on the electronic component on the circuit board, the noise protection sheet is carried together with the carrier tape, and adsorbed using e.g. an adsorption collet and moved from the carrier tape onto the electronic component on the circuit board. In this state, the extending portion of the metallic sheet is fixed to the grounding terminal for the circuit board. In this case, all the components constituting the mounting apparatus may be existing equipment and operating machines. This permits the noise protection sheet to be automatically mounted on the electronic components without increasing the production cost.
In accordance with the third embodiment of this invention, there is provided a method for mounting an noise protection sheet on an electronic component loaded on a circuit board, the noise protection sheet with a metallic sheet sandwiched by insulating films from its both front and rear surfaces, comprising: a carrying step of carrying the noise protection sheet held on a carrier tape; a moving step of adsorbing the noise protection sheet and moving it from the carrier tape onto the electronic component on the circuit board; and a soldering step of soldering an extending portion formed at the one end of the metallic sheet to a grounding terminal of the circuit board.
This mounting method permits the noise protection sheet provided by the first aspect of this invention to be easily mounted on the electronic component of the circuit board and hence can give a sure solution to the noise problem.
The above and other objects and features of this invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.